The present invention relates to an apparatus for measuring the percentage of moisture content and the weight of a sheet-like object. The object is inserted into a cavity resonator and a percentage of moisture content of the sheet-like object is measured by detecting a variable and attenuated resonant voltage of a microwave introduced into the cavity resonator. Further, the weight of the sheet-like object is measured by detecting a variable resonant frequency of the microwave introduced.
Typically, separate measuring system are used for measuring the moisture content or percentage of moisture content and the weight per unit area of sheet-like objects for indicating the quality of the objects. For example, to measure the percentage of moisture, infrared rays or microwaves are used to irradiate an object to be measured and the amount of the attenuated wave is measured. To measure weighing, .beta. rays or X rays are used to irradiate the object and an amount of the rays transmitted through the object is measured.
As described above, the conventional measuring apparatus of this type needs two independent measuring systems with different irradiating sources, so that the measuring apparatus is bulky and expensive. Because of use of .beta. or X rays is hazardous to the human body, the conventional measuring apparatus further needs protective devices for protecting the human body from exposure. The use of two measuring systems further makes it difficult to measure a paper making process in an on-line manner.